PROJECT SUMMARY (ABSTRACT) Alzheimer's Disease and related disorders represent a huge public health and health care burden, prompting innovative research of modifiable risk factors. The search for modifiable predictors of dementia has turned towards environmental exposures. Prior research suggests air pollution accelerates cognitive decline in older populations. But this research has major gaps. Few studies have used longitudinal measures, nor have they been nationally-representative. Additionally, there's an urgent need for studies that more comprehensively account for socioeconomic position (SEP). While it is known that cognitive outcomes vary by SEP, the joint effect of air pollution and SEP remains largely unknown. Our study proposes to explore the impact of air pollution (PM2.5) on cognitive decline, and the potential for interaction between air pollution and SEP. Air pollution exposure varies by SEP; more disadvantaged individuals are exposed to more air pollution. Accounting for SEP is important when evaluating the effects of air pollution on cognition. Further, we believe that the effect of air pollution on cognition outcomes is different for those with high SEP compared to those with lower SEP. I'm submitting my proposal for consideration in order to support my dissertation research, with the overall goal of furthering study of environmental and social determinants of cognitive aging and dementia. The overall objective of this application is to determine if and how air pollution and SEP influence cognitive decline. My specific aims are as follows: Aim 1 assesses the relationship between air pollution and cognitive level and decline in the National Health and Aging Trends Study (NHATS). Started in 2011, NHATS follows a nationally-representative population of Medicare patients 65 years and older, with annual, in-person cognitive assessments. By linking aerosol optical depth models estimating air pollution to individual-level NHATS data, we can model long-term exposure to PM2.5 among NHATS participants. Aim 2 examines the joint effect of air pollution and SEP on cognitive level and decline in NHATS. SEP will be measured as education, income, financial strain, and neighborhood-SEP. Advanced statistical methods, including multi-level modeling of individual and census-tract level change, will provide a strong basis for understanding effects of air pollution on cognitive aging. This study presents a timely opportunity to contribute to emerging literature on how environmental and social exposures interact to shape cognitive function over time in older adults. Because policy reforms can potentially target either or both environmental and social factors, the findings of this research proposal can inform decision-making, benefitting those most likely affected. With the support of my terrific mentorship team? experts in cognitive aging and dementia, social determinants of health, and air pollution exposure?this proposal will contribute to predictors of cognitive aging research, and enhance skills required for me to further this area in subsequent research.